The present invention relates generally to MIMO transceivers, and more particularly to antenna matching for MIMO transceivers.
Wireless communication systems often use multiple antennas at the transmitter and receiver to improve communication performance. Such Multiple-Input, Multiple-Output (MIMO) systems offer significant increases in data throughput without increasing the bandwidth or transmit power requirements.
MIMO transmitter antennas experience crosstalk due to mutual coupling between the antennas when a signal transmitted by one antenna couples to, and is therefore received by, one or more of the other transmit antennas. Such crosstalk effectively couples the transmitters, which may cause various transmitter problems, e.g., back intermodulation interference at the transmitter output terminals, transmitter mismatch, efficiency loss, etc. Base station transmitters may reduce and/or eliminate the mutual coupling by physically separating the antennas to spatially isolate the antennas. However, some wireless devices cannot adequately spatially separate the antennas. For example, mobile devices typically do not have sufficient space to adequately separate the antennas. When the antennas cannot be sufficiently separated, other techniques should be used to decouple the transmitters.